Abstract
Leveraging the unique surface expression of heat shock protein 90 (Hsp90) in breast cancer provides an exciting opportunity to develop rapid diagnostic tests at the point-of-care setting. Hsp90 has previously been shown to have elevated expression levels across all breast cancer receptor subtypes. We have developed a non-destructive strategy using HS-27, a fluorescently-tethered Hsp90 inhibitor, to assay surface Hsp90 expression on intact tissue specimens and validated our approach in clinical samples from breast cancer patients across estrogen receptor positive, Her2-overexpressing, and triple negative receptor subtypes. Utilizing a pre-clinical biopsy model, we optimized three imaging parameters that may affect the specificity of HS-27 based diagnostics – time between tissue excision and staining, agent incubation time, and agent dose, and translated our strategy to clinical breast cancer samples. Findings indicated that HS-27 florescence was highest in tumor tissue, followed by benign tissue, and finally followed by mammoplasty negative control samples. Interestingly, fluorescence in tumor samples was highest in Her2+ and triple negative subtypes, and inversely correlated with the presence of tumor infiltrating lymphocytes indicating that HS-27 fluorescence increases in aggressive breast cancer phenotypes. Development of a Gaussian support vector machine classifier based on HS-27 fluorescence features resulted in a sensitivity and specificity of 82% and 100% respectively when classifying tumor and benign conditions, setting the stage for rapid and automated tissue diagnosis at the point-of-care.
Highlights
Breast cancer management represents a complicated landscape, with therapy regimens often including a mélange of chemotherapy, radiation therapy, and surgical procedures
We found that HS-27 labels all receptor subtypes of breast cancer, but not normal cells, and binds to Hsp[90] expressed on the surface of breast cancer cells before being internalized
We further demonstrated that HS-27 can be used to treat aggressive Her2+ and triple negative (TNBC) breast cancers by degrading an Hsp[90] client protein involved in cell metabolism, down-regulating both glycolytic and oxidative metabolism leading to decreased cell proliferation
Summary
Breast cancer management represents a complicated landscape, with therapy regimens often including a mélange of chemotherapy, radiation therapy, and surgical procedures. In high-income countries (HICs), when a woman presents with a suspicious lesion on her mammogram, she undergoes diagnostic biopsy to determine what type of lesion is present by pathological analysis. This strategy is not adoptable by LMICs, due to the scarcity of pathologists. With optimized imaging parameters of a 1 to 10-minute post-excision window, 1-minute incubation time, and 100 μM dose, we demonstrated the feasibility of our imaging strategy on standard of care biopsies from patients presenting with a mammographic lesion, as well as a population of patients undergoing breast reduction mammoplasty to interrogate HS-27 uptake by normal breast tissue. We employed image processing methods to extract HS-27 fluorescence features to differentiate tumor from benign tissues
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